In the domain of automatic selection of food products, the technique of discarding the defects is known according to three different principles, which can be summarized as:                Expulsion by air jet.        Mechanic expulsion with pneumatic control.        Expulsion by suction tubes.        
Of course each of these solutions is well suited to particular products and related defects, in order to obtain the maximum discarding efficiency with the minimum value of false discard.
The finding here described and claimed, concerns products with high content of water/juice, which therefore must be discarded via suction.
The known technology requires distributing the product on a carpet, if possible in a single layer (for cubes) or in a layer of adequate thickness in the case of pulps.
These expulsion systems and groups are applied downstream of the so-called selection machines which, by means of a suitable optic-electronic part, actually control the discarding group.
For simplicity purposes, the electronic selector is composed of video cameras which frame the product passing on the carpet, the product being illuminated by a light group with specific wavelengths.
The collected signals are elaborated by a vision board, which—based on the comparison with pre-settable threshold parameters—activates the expulsion group in the area where the defect is passing.
The suction expulsion group is composed of a central collector tube, of varying size, which laterally bears a certain amount of suction ports, usually positioned in two rows, in quincunx position as shown in FIG. 1 of the known art.
A cylinder or an electric actuator controls a shaft which at its end bears a bushing/valve which, by sliding vertically, connects the central manifold (where the vacuum is applied) to a suction port. In idle position, the valve or bushing closes the communication hole, whereas it opens it when in suction position.
The product is spread and distributed at a certain distance from the resting bushing; the bushing descends approaching the carpet and opening the communication port.
At this point there are drawbacks, related to the fact that suction already begins when the bushing/valve starts to open the communication duct (passing in front of the hole of its suction manifold): in a time diagram regarding the suction action in the carpet area, there is shown that at first there's no depression (duct completely closed), then while the duct is being opened along the descending path of the valve/bushing, it can be observed that the suction action on the carpet area begins.
Therefore there is a depression curve that reaches its maximum at the complete opening (and stays like that for a definite time), then returns to zero symmetrically; this leads to suction phenomena adapted to create turbulences already during the bushing descending step; it follows that, being the bushings adjacent one to the other, they can interfere one another in their operating step, or at least the operating actuator can modify the position of the adjacent defects or even move the product, in case the latter is light. Moreover, the quantity of sucked material exceeds the desired amount, since the step starts before the supposed time.